In recent years, organic light-emitting diode (OLED) display panels becomes very popular in the world since OLED display panels feature self-illumination, wide view angle, short response time, high lighting efficiency, wide color gamut, thin thickness, large size, flexibility, simple fabrication, and low cost.
Presently, in an OLED display panel, a pixel define layer (PDL) is formed by coating, exposure, development, and baking processes. Wherein, the top surface of the PDL is hydrophobic and the side surface of the PDL is hydrophile. When an organic electroluminescent device is fabricated, ink formed by function layers is printed on the PDL. Thus, the thickness of the PDL is thicker from center to edge, thereby resulting in non-uniform brightness when current flows through the edges of the function layers.